1. Field of the Invention
The present invention relates to the field of heat pumps and methods of operation of same. In particular, the present invention relates to heat pumps which employ as part of their cycle the adsorption and desorption of a fluid, such as ammonia.
2. The Prior Art
Adsorption heat pumps operate on the principle that certain materials which are contained in a reactor (reactor materials), are capable, at certain temperatures and pressures, of adsorbing other materials (reactant materials), in a reaction which gives off heat. These same reactor materials are also capable of desorbing the reactant materials, when heated sufficiently. The reactor is connected in a circuit with a condenser and an evaporator. The heat exchange properties of the reactor material can be taken advantage of in heat exchangers, thermally connected to the evaporator and condenser, in which one or more working fluids exchange heat with the reactant materials. The working fluids, in turn can be employed in compression/condensation - expansion/evaporation systems for heating and/or cooling a residence, for example.
Single reactor materials in an adsorption heat pump are typically solids, but may also be liquids (e.g., Dehne, U.S. Pat. No. 5,237,839). A common reactor material is the substance known as zeolite, which may either be natural or artificially made. The reactant materials are typically fluids, which may undergo a phase change from liquid to vapor, to liquid again, during the operating cycle of the pump. Water is often used as the reactant with a zeolite reactor material, or ammonia is used as the reactant with an activated carbon reactor material.
Typical prior art adsorption heat pump systems utilize two reactors, such that as one reactor is adsorbing reactant, the other is in the process of desorbing reactant. Other prior art systems may have more than two reactors, each in a phase of the reaction cycle separate from the phases of the other reactors. Such systems have been used in an attempt to provide a more or less continuous supply of heating or cooling, or in some applications, simultaneous heating to one location and cooling to another location.
Rothmeyer, U.S. Pat. No. 4,594,856; Tchernev, U.S. Pat. No. 4,637,218; Rothmeyer, U.S. Pat. No. 4,754,805; Yonezawa et al., U.S. Pat. No. 5,024,064; Rockenfeller, U.S. Pat. Nos. 5,025,635, 5,161,389, 5,241,831, and 5,263,330, all show examples of two (or more) reactor systems. However, two reactor systems may have the potential drawback that the heating and cooling of the reactors, using a heat transfer fluid, may tend to require large heat transfer surfaces.
One reactor systems are known in the prior art, and are typically used for so-called thermal storage. That is, heat or power is used to drive an adsorption or desorption process, and the heat which is given off or taken in is later released for the dedicated heating or cooling, only, of a space. Such a system is disclosed in Mitani et al., U.S. Pat. No. 4,742,868. A single reactor system which is capable of simultaneous heating and cooling is disclosed in Yonezawa et al., U.S. Pat. No. 5,005,371. Single reactors which use a heat transfer fluid also require large heat transfer surfaces.
It is desirable therefore to provide a heat pump configuration which has an improved method of heating the reactor which does not require large heat transfer surfaces.
It is also desirable to provide a heat pump configuration which uses only a single reactor, which could have the effect of improving cycle efficiency.